Yuxin He,Qiuyu Chen,Song Yang,Chang Lu,Mengting Feng,Yuanli Jiang,Guoxi Cao,Jianping Zhang,Chuntai Liu
The epoxy nanocomposites with Fe 3 O 4 modified graphene oxide (Fe 3 O 4 /GO) were used to influence the micro-cracks resistance of carbon fiber reinforced epoxy (CF/EP) laminate at 77 K. Fe 3 O 4 /GO with good paramagnetic properties were prepared by co-precipitation method and used to modify epoxy for cryogenic applications. Fe 3 O 4 /GO modified CF/EP laminates were also prepared through vacuum-assisted resin transfer molding (VARTM). The results show that the Fe 3 O 4 /GO can effectively improve the mechanical properties of epoxy (EP) matrix at 77 K and reduce the coefficient of thermal expansion (CTE) of EP matrix. It also can obviously improve the micro-cracks resistance of CF/EP composites at 77 K. Compared to neat EP, the CTE of Fe 3 O 4 /GO modified EP composite is decreased 51.6%. Compared to CF/EP composite, the micro-cracks density of Fe 3 O 4 /GO modified CF/EP composite at 77 K is decreased 60.0%.
For more practical applications, research on magnetic refrigeration has been gradually focused on developing refrigerants with large magnetocaloric effect (MCE) under low magnetic fields (≤2 T). EuTiO 3 exhibits considerable low-field MCE near ordering temperature, meanwhile the magnetic switch from antiferromagnetic to ferromagnetic (AFM-FM) in it provides the feasibility of improving the magnetocaloric performance. In this study, a series of Eu(Ti,Nb,M)O 3 (M=Cu or Zn) compounds were synthesized, and the crystal structure, magnetic properties together with cryogenic MCEs were investigated in detail. The co-substitution contributes to an FM coupling domination in all the compounds. Besides, significantly enhanced and giant low-field MCEs were detected in these compounds. Under the field change of 1 T, all the samples possess remarkable magnetic entropy change (>15 J·kg -1 ·K -1 ) around 5 K without hysteresis. The corresponding refrigerating capacities are calculated to be 68.0, 72.6, 76.0, and 69.6 J·kg -1 , respectively, exhibiting an increase of 149–178% than EuTiO 3 . The outstanding magnetocaloric performances make the Eu(Ti,Nb,M)O 3 (M=Cu or Zn) compounds competitive candidates for cryogenic magnetic refrigeration.
In this study, the phase diagrams for the binary systems of n-C11H24–n-C14H30, n-C12H26–n-C13H28, n-C12H26–n-C14H30, and n-C13H28–n-C15H32 were experimentally investigated to employ potential phase change materials (PCMs) for cryogenic applications. Besides, the phase diagrams were theoretically obtained on the basis of the ideal solubility and UNIFAC models, and the UNIQUAC, Wilson, and NRTL models were applied to build correlations between experimental and predicting values. The results show that the compositions of the eutectic points appear at 10 wt % C14 for the C11–C14 system, 17.8 wt % C13 for the C12–C13 system, 18 wt % C14 for the C12–C14 system, and 10 wt % C15 for the C13–C15 system with eutectic temperatures of 246.85, 257.75, 260.45, and 265.55 K, respectively. Moreover, the melting temperatures calculated using the theoretical models are in good agreement with the experimental results. The average relative deviations for the C11–C14 system and C13–C15 systems are merely 0.3814% and 0.3220%, respectively, by using the NRTL model. Simultaneously, the minimum relative deviations for the C12–C13 and C12–C14 binary systems are 0.3649% for the ideal solubility model and 0.4856% for the UNIFAC model. Finally, upon comparing the predicted results of the studied binary systems using the results of the five models, we find that the UNIFAC model provides the most accurate results for the melting temperatures.
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